Theme B

How are ocean circulation, ice cover, heat and carbon uptake and biogeochemistry impacted by the ozone hole?

Accumulating evidence suggests that, through effects on surface winds, stratospheric ozone levels impact sea-ice, ocean circulation, transport and biogeochemistry. But little is known regarding the processes involved, exactly what changes have occurred, and how the system will evolve as ozone recovers.

Specific research thrusts include:

Computing climate response functions for the ozone hole.

Understanding impacts on ocean tracer transport and biogeochemistry.

Determining if atmosphere-ocean coupling affects the surface response to ozone depletion and recovery.

Key results to date:

Modeling indicates that Antarctic sea surface temperatures (SSTs) will respond differently at different time scales to the annual opening and closing of the ozone hole. Cooler summer SSTs induced by enhanced northward Ekman drift now lead to early winter freezing and expanding sea ice coverage, but over years to decades SSTs will slowly warm overall in response to upwelling of warm water from the interior ocean driven by stronger westerly winds leading to reductions in sea ice extent year-round.Ferreira et al. 2015>

Observations show robust changes in the Southern Ocean in recent decades. Using a comprehensive chemistry-climate Earth system model, we show that increases in ozone-depleting substances during the late 20th Century are likely to have been an important driver of these changes, causing a poleward shift of the ocean's meridonal overturning circulation as well as changes in temperature and salinity.Solomon et al. 2015>

Differences between various Earth System models in how Southern Ocean winds trends are simulated may be less important for carbon uptake performance than differences in how mesoscale eddies are parameterized.See Gnanadesikan et al. 2015>